Installing an upgrade of a computer program on a personal computer generally requires a user to load a compressed version of the program onto the computer and begin an installation process. The installation process normally requires a user to execute an installation program and additionally respond to prompts for information as required by the installation program. The installation process may directly overwrite the previous version of software or the process may uninstall the current version of the software prior to installing the new version. Once the software is installed the system is typically rebooted and an attempt can be made to run the software. If the software fails to install, the user must decide whether to reinstall the upgraded program or to reinstall the previous version that was compatible with the system.
In a networked system, which is connected to a central server with attached disk arrays, an upgrade to a centrally accessed program on the server is performed in a substantially similar fashion, where the upgrade requires that the system administrator load the upgrade, install the program, and reboot the server. The system must be shut down for a period of time during installation and the rebooting of the server. This shutdown makes access to both files and programs on or connected to the server impossible during rebooting. Additionally, if the upgrade fails to install, the system administrator must decide whether to reinstall the upgrade or the current version of the program. Both operations again take the server offline and deny users access to files and programs.
In a system which has redundant servers, upgrading a program posses a further problem. In order for the redundant servers to operate properly, the program mirrored on the inactive server must be compatible with the upgraded program on the active server. Potential inconsistencies may occur when the active server is upgraded with a new version of a program and the format of data transfer between the two servers changes. In such a circumstance redundancy is lost between the servers. Also if an upgraded active server goes off line and the inactive server becomes active the inactive server may not be capable of interpreting the new message protocols that were part of the upgraded server program.